"I hope we can avoid that because to have a further election is to effectively have the same configuration of parties and number of seats coming back here," he said.

Alliance does not have the electoral strength to take a ministerial seat in the powersharing coalition by right, but it has again been offered the politically sensitive justice portfolio because the two leading parties - the Democratic Unionists and Sinn Fein - do not want each other to have the job.

Since the devolution of justice powers to Belfast in 2010, that mutual veto has been overcome due to the fact both main parties were content for the cross-community Alliance Party to take the job.

But in the wake of this month's Assembly election, Alliance has made clear it will only re-take the post if the DUP and Sinn Fein agree to implement a series of policy demands around issues like tackling segregation and combating paramilitarism.

Negotiations between the parties are on-going ahead of a deadline for forming a government next Wednesday. A crunch meeting is scheduled for tomorrow, when Alliance's wish list will be discussed.

Mr McGuinness said he hoped ministries would be allocated and a government formed on Wednesday next week.

The SDLP, which is eligible for one ministerial post by right, also remains in negotiations to form the executive, but it is unlikely both the DUP and Sinn Fein would support the nationalist party taking on the justice job.

Mr McGuinness said he remained hopeful an administration would be formed that included both the SDLP and Alliance.

The Ulster Unionists have already announced their intention to take up the recently established option of forming an official opposition.

"I think people need to get real, it's make your mind up time over the course of the next seven days," said Mr McGuinness.

He added: "My focus at the minute is on whether the Alliance Party decide to take the position they have been offered, if they take it then that's a good result, I think, for everybody.

"We should also be very clear that if they don't take it that could present major problems."

DUP First Minister Arlene Foster has already made clear her party would not consent to Sinn Fein taking the post.

Given the DUP leader's stance, her republican partners in government are highly unlikely to support a DUP incumbent.

Mr McGuinness would not be drawn on that specific question at Stormont Castle on Wednesday.

"I am not making any comment whatsoever on what I will or will not support in the event that the Alliance Party turn down the offer they have been made," he said.

Mr McGuinness commented on the state of negotiations after having a meeting at the castle with the Irish government's reappointed Minister for Foreign Affairs Charlie Flanagan.

Alliance has insisted it will only fill the role again if it achieves progress on five key policy issues - building an integrated society; funding of services, not division; "cleaning up" of politics; investment in jobs, skills and the economy; and ending all forms of paramilitarism.

While the DUP and Sinn Fein have until next Wednesday to form a new administration - something that will be impossible without a justice minister - Alliance wants to see progress before Thursday evening, when its ruling council is due to meet to discuss the issue.

If Alliance follows the UUP lead and refuses to join the new administration, then the two main parties will have to find another agreed minister - or else an executive cannot be formed.

In that context, the Green Party - which has two seats in the 108-seat legislature - has been mooted as a potential alternative.

Green party leader Steven Agnew has not ruled himself out as a potential minister, but said the conditions would have to be right.